Precision grinding machine



y 1954 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE Filed March 29, 1962 12 Sheets-Sheet 1 INVENTORS HARRY E LUEBKEMANN JACOB DECKER ALBERT H. DALL ATTORNEYS July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE l2 Sheets-Sheet 2 Filed March 29, 1962 July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE l2 Sheets-Sheet 3 Filed March 29, 1962 July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE 12 Sheets-Sheet 4 Filed March 29, 1962 I-IPF'I July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE 12 Sheets-Sheet 5 Filed March 29, 1962 www July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE Filed March 29, 1962 12 Sheets-Sheet 6 y 1954 H. E. LUEBKEMANN ETAL 3,141,257

PRECISION GRINDING MACHINE Filed March 29. 1962 12 Sheets-Sheet 7 July 21, 1964 H E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE Filed March 29, 1962 12 Sheets-Sheet 8 y 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE Filed March 29, 1962 12 Sheets-Sheet 9 July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,267

PRECISION GRINDING MACHINE Filed March 29, 1962 12 Sheets-Sheet 10 July 21, 1964 H. E. LUEBKEMANN ETAL 3,141,257

PRECISION GRINDING MACHINE Filed March 29, 1962 12 Sheets-Sheet 12 United States Patent 3,141,267 PRECISION GRINDING MACHINE Harry E. Lnebkemann, Jacob Decker, and Albert H. Dal], ail of Cincinnati, Uhio, assignors to The Cincinnati Miliing Machine (10., Cincinnati, Ohio, a corporation of Ohio Filed Mar. 29, 1962, Ser. No. 183,538 24 Claims. (Cl. 51-165) This invention relates to a machine tool and more particularly to a precision grinding machine for finishing workpieces to extremely close tolerances.

Recent advances in technology relating to servo control mechanisms such as missile guidance and control systems has created a demand for machine tools which will finish workpieces to tolerances in the magnitude of a few millionths of an inch. In order to produce workpieces which are consistently within such tolerances, the machine tools employed to operate on the workpieces must be built with the capacity to produce correspondingly accurate movements of the tool carrier. At the same time, the rate of movement must be slow enough to prevent the creation of excessive forces between the cutting tool and the workpiece which would spring and distort either the machine or the workpiece beyond allowable tolerances. In producing extremely slow movement of a tool carrier, another problem, that of stick-slip between relatively movable members, becomes very important.

An object of this invention is to provide an extremely accurate grinding machine capable of consistently machining workpieces to tolerances of a few millionths of an inch.

An object of this invention is to eliminate the stickslip problem in the movement of a grinding wheel at greatly reduced feed rates.

A further object of this invention is to provide a grinding machine having a wheelhead of unique construction which facilitates the movement of a grinding wheel at a rate slower than has been practical heretofore.

Still another object is to provide a grinding machine in which a fixed amount of force acting quickly on the grinding wheel spindle carrier will produce the same very small amount of movement of the grinding wheel each time the same force is applied.

Another object of this invention is to provide a grinding machine with a wheelhead having two portions relatively movable without the occurrence of stick-slip motion therebetween.

Yet another object is to provide a feed mechanism to produce an extremely slow rate of movement of a machine tool member.

It is an object of this invention to provide a machine tool feed mechanism that will produce a series of very small increments of movement of a member.

It is also an object of this invention to provide a grinding machine with a pickfeed that is infinitely variable between a maximum value and a minimum value approaching zero movement.

An object of this invention is to provide a feed mechanism in one part of a split wheelhead of a grinding machine which is independently operable to effect a tilting of one part of the wheelhead relative to the other part at an ultra fine rate of movement.

A still further object is to provide a grinding machine having two separate feed mechanisms successively operable to move the grinding wheel in a machining cycle that includes a conventional feed movement followed by an arcuate swing of the grinding wheel at a greatly reduced rate.

An object of this invention also is to provide a grinding machine having an automatic infeed mechanism which is operable to minimize the stresses created between the workpiece and grinding wheel in accordance with the approach of a workpiece to final size.

An additional object is to provide an ultra precision grinding machine with a gauge controlled, interrupted grinding wheel feed cycle to relieve grinding pressure during infeed before the final infeed movement is completed.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

A grinding machine constructed in accordance with the preferred form of this invention has a grinding wheel carriage or wheelhead slidably supported for movement toward and away from a worktable in the conventional sliding manner. The wheelhead is split into two portions, however. The lower portion is received on the base for conventional sliding movement. An upper portion which defines the grinding wheel spindle housing is fixed on the lower portion by means of stiif reed springs. The reed springs are fixed between the upper and lower portions at their forward end nearest the worktable. When the rearmost end of the upper portion is lifted, the upper portion is tilted relative to the lower portion. The axis on which the upper portion tilts passes through the reed springs which are flexed to allow the tilting movement. The axis of rotation of the grinding wheel spindle is spaced from the axis of tilt. Therefore, by tilting the upper portion toward the worktable, the grinding wheel is caused to swing in an arc toward the worktable. This swinging motion is utilized as an ultra fine feed which is not affected by the stick-slip phenomenon. The entire relative motion between the upper and lower portions is accomplished by the flexing of the reed springs and there is no relative sliding motion between the upper and lower wheel head portions. The total amount of tilt feed of the grinding wheel is very small, being measured in thousandths of inches. Consequently, the total flexing of the reed springs is very small and their elastic limit is never approached. Thus, each time the springs are flexed, the same lifting force will produce the same tilt of the upper portion.

The feed mechanism which lifts the upper portion is a high mechanical advantage device which utilizes an overrunning clutch to rotate a shaft having an eccentric diameter portion. The clutch is reciprocally rotated to produce a series of increments of rotation of the shaft in one direction. The arcuate length of the clutch stroke is adjustable to any amount between a predetermined maximum and zero. Since the rotary stroke is infinitely variable between extremes, the ultra fine feed rate is infinitely variable between extremes. In the preferred form, the overrunning clutch is releasible to allow free relative rotation of the drive shaft and clutch. Therefore, the feed shaft may be rotated in the opposite direction by a reset mechanism at the completion of a grinding operation. The reverse rotation of the feed shaft retracts the grinding wheel from the workpiece and resets the upper wheel head portion back down on the lower portion.

Control of the grinding machine feed mechanism is by electro-hydraulic means which includes an in-process gauging device. The gauging device controls the complete infeed grinding cycle. It is used to provide a pause in the infeed movement to allow the grinding pressures to be relieved prior to the final feed movement of the grinding wheel. The final feed results in movement of the grinding wheel a very short distance and is accom- I swivel table 16.

-movement toward and away from the .table 12. abrasive grinding wheel 32 is rotatably supported in the plished by the tilt feed mechanism. The workpiece is reduced to final size during the final feed movement at which time the wheelhead is retracted to withdraw the grinding wheel from the workpiece.

, A clear understanding of this invention may be obtained from the following detailed description in which reference is made to the attached drawings wherein:

FIG. 1 is a front elevation of a grinding machine. FIG. 2 is a left side elevation of the machine in FIG. 1. FIG. 3 is a section of FIG. 1 on line 3--3. FIG. 4 is a section of FIG. 3 on line 4-4. FIG. 5 is a section of FIG. 3 on line 5-5. .FIG. 6 is a section of FIG. 3 on line 6-6.

FIG. 7 is a top elevation, partly in section, of the clutch shown in section in FIG. 5.

FIG. .8 is asection of FIG. 3 on line 8-8. FIG. 9 is a section of FIG. 10 on line 99.

FIG. 10 is a section of FIG. 9 on line lit-10 and is the lower portion of .the wheelhead of FIG. 3.

.FIG. 11 is a sideelevation of the wheelhead handwheel mechanism partly in section.

FIG. 12 is a section of FIG. 11 on line 1212. FIG. 13 is a vertical section of the plunge feed mechanism at the rear of the grinding machine below the wheelhead.

FIG. 14 is a section of FIG. 13 on line 1414. FIGS. 15 and 16 are schematic hydraulic diagrams. FIG. 17 is a schematic electrical control diagram. FIG. 18 is a side elevation of the footstock and gauge mechanism.

The Machine in General The general appearance of a centertype grinding machine constructed in accordance with the preferred form of this invention is shown in FIGS. 1 and 2. The machine is built in and around a base 10. A carriage 12 which defines a reciprocally movable table is slidably supported on ways 14 (FIG. 11) in the top of the front of the base10. A swivel table 16 is fixed on top of the table '12 and is releasable for pivotal adjustment to create an angular relationship between the longitudinal axis of the swivel table 16 and the ways 14. A headstock 18 and a foot stock 29 are attached to opposite ends of the Centers 22, 24 extend toward each other from the head and foot stocks 18, 20, respectively.

The centers 22,24 are adapted to support a workpiece therebetween during a grinding operation. Both the head and foot stocks 18, are releasable for longitudinal adjustment along the swivel table 16 by operation of clamps 19 and 21. Various lengths of workpieces may then be accommodated by the-machine. A motor 26 is attached to the top of the headstock 18 for rotation of a driver 28 around the center 22. The driver 28 is adapted to engage a dog (not shown) which would extend from a workpiece. i tween the centers 22, 24 would be rotated during a grind- By this means, a workpiece received being-operation. The table 12 is mechanically connected Awheelhead 30 is slidably received on the base 10 for An wheelhead 30. Itis partially covered by a wheelguard -34. A motor 36 is mounted on top of the wheelhead 30 and is connected through a belt drive 37 (FIG. 3) to the wheel spindle '39. The wheelhead 30 is moved toward and away from the table 16 by operation of a feed mechanism contained in the unit 38 at the rear of the machine and tobe described subsequently herein. 30 is also connected to the handwheel 40 for movement The wheelhead for control of the automatic grinding cycles. The gauge unit 44 is of the air electric type used for in-process gauging, that is, a workpiece is measured while it is ground. These gauges are well known in the machine tool industry. The gauge calipers 46, FIGS. 1, 18, are swingably mounted on top of the footstock 20 for movement into contact with and away from a workpiece 11 supported between centers 22, 24.

The gauge calipers 46 are comprised of a support 43 in which a pair of adjustable jaws 45, 47 are received. Each of the jaws 45, 47 extends to close proximity with a workpiece 11, the jaws being on opposite sides of the workpiece. Air under closely regulated pressure. issupplied to the passage 13. Each of the jaws 45, 47 has an air passage 15, 17, respectively, in communication with the passage 13. The passages 15,17 terminate in small orifices adjacent to and closely spaced from the workpiece 11. The pressure in the passage 13 is controlled by the escape of air from the tWo passages 15, 17. The passage 13 is connected back to the gauge unit 44, FIG. 1, where it is in communication with a plurality of pneumatic relays. Each of these relays controls the condition of electrical contacts operated thereby in accordance with the back pressure in the passage 13. Each of the pneumatic relays is set to operate at a, pressure ditferent from the pressure at which the others operate. The operation of pneumatic relays in a similar back pressure gauge sys tem is described in U.S. Patent 2,969,623 issued January 31, 1961 on application filed by K. D. Mehlhope and A. H. Faulhabcr. The electrical circuit in which contacts of the gauge are used is described in detail in the description of electrical operation discussed in a subsequent section of this specification.

The Wheelhead Stick-slip is basically a problem arising in systems where members are relatively slidable one on another. In a system where a movable object such as a grinding machine wheelhead has considerable weight and the rate of movea motion. Devices such as ball bearing ways have not been satisfactory to solve the problem since there is an inherent component of sliding friction due to deformation of L the balls and ball tracks as the balls are moved therealong and pure rolling contact is not achieved although the problem is somewhat minimized. Ball bearing systems present another problem in that they do not have the damping qualities which are necessary to suppress chatter vibrations in a grinding machine unless the balls are preloaded. In preloading the balls, the component of sliding friction is increased and the stick-slip is likewise increased. Moreover, in preloading the bearings, stresses are introduced in the machine which can affect the accuracy and repeatablity of the machine, especially in jobs where extreme accuracy is required. For these reasons,

' the preferred embodiment of the grinding machine utilizes a unique wheelhead construction to eliminate stick slip in the final movement of the grinding wheel 32.

A longitudinal section of the wheelhead 30 is shown in FIG. 3. The wheel head 30 is comprised of two portions.

' The lower portion 48 rests directly on ways 50, 52 (FIG.

10) in the rear of the base 10 and is slidably movable toward and away from the table 16 (FIG. 2). The upper portion 54 of the wheelhead 30 defines a spindle housing in which the grinding wheel spindle 39 is supported for high speed rotation by the motor 36 (shown in FIG. 1 but in the mounting plate 33 and threadedly engaged through a pin 41 that is fixed in the cover plate 49. Thus by rotation of the screw 35, the mounting plate 33 together with the motor 36 can be positioned on the wheelhead 3t) to put the belts 37 under the proper tension.

The upper portion 54 of the wheelhead 3% is attached to the lower portion 48 by a set of relatively stiff reed springs 55, 55. The spring 55 is fixed between the front ends (the end toward the table 12) of the upper and lower portions by machine screws 57, 58. The spring 55 is centered between the sides of the wheelhead 30 and is arranged to bend away from a vertical axis when the upper portion 54- is tilted. The bending of the spring occurs at the reduced section area 55a. On either side of the spring 55 are the reed springs 56 which are fixed between the upper and lower portions 48, 54 and are designed to bend away from a horizontal axis when the upper portion 5-:- is tilted. The springs 56 are also adapted to bend at reduced section areas 56a which are in line with the reduced section areas 55a of the spring 55. A line through the centers of the reduced section areas 55a, 56a then defines the axis about which the upper portion 54 tilts when the rear of the upper portion is lifted.

The spindle 39 is spaced from the springs 55, 56 and therefore, as the upper portion is tilted, the grinding wheel 32 is swung in an arc. The upper portion 54 is fixed to the lower portion 43 only by the springs 55, 56. The weight of the upper portion 54 as well as the tension in the belt 37 tend to tilt the upper portion clockwise as viewed in FIG. 3. A pair of springs 59, 60 (FIG. 8) are compressed between the cover plate &9 and the rear end of the upper portion 54 and these, too, tend to rotate the upper portion 54 clockwise. A bushing 61 is fixed in the upper portion 54 at its rear and defines a ball socket which receives a ball end pin 62 that rests on a lever 63. The lever 63 controls the elevation of the rear of the upper portion 54. The forces tending to rotate the upper portion 54 clockwise will hold the bushing 51 firmly on the pin 62 and as long as the lever 63 is stationary on the lower portion 48, the upper and lower portions 48, 54 act as a single unit Wheelhead. The upper portion 54 will tilt toward the worktable only when the lever 63 is raised.

The T ill Feed Mechanism The mechanism which is operable to raise and lower the lever 63 (FIGS. 3 and 4) is contained in the lower portion 48 of the wheelhead 36. The lever 63 is pivotal on a ball 64 (FIG. 4) seated in a socket 65 fixed in the lower portion 48. The ball end pin 62 is received at one end in a socket in the lever 63 which is off-set from the ball 64- to provide a short lever arm from the pivot of the lever 63. The other end of the pin 62 is received in the socket bushing 61 that is fixed in the rear of the upper wheelhead portion 54. The end of the lever 63 opposite the ball 64 is pushed downward by a spring 66 which is compressed between the lever 63 and the cover plate 49. The spring 66 produces a force which tends to rotate the lever 63 counter-clockwise around the ball 64. Therefore, the lever 63 is held firmly against the slightly eccentric diameter portion 67a of the tilt feed shaft 67.

As shown in MG. 3, the tilt feed shaft 67 is rotatable in bearings 63, 69 that are received between the shaft 67 and a bushing 7t} fixed in the lower wheeihead portion 43. An overrunning clutch mechanism 71 is received on one end of the tilt feed shaft 67. The clutch 71 is an overrunning sprag type clutch which engages with the clutch bushing 72 that is keyed to rotate with the shaft 67. As shown in FIG. 5, the clutch 71 is comprised of a casing member 73 which is adapted to be rotated relative to the lower portion 48 a limited amount. Inside the casing 73 is a cylindrical sprag pin 74 which is held in close proximity with the bushing 72 by an adjustable plunger 75. The sprag pin 74 is held in concurrent contact with the face of the plunger 75 and the bushing 72 by a spring loaded plunger 76 which tends to move the sprag pin 74 toward the fixed pin 77. As shown in FIGS. 6 and 7, the fixed pin 77 is attached to a bracket 78 that is fixed to the lower portion iii by machine screws 79, 8t). The pin 77 then is fixed relative to the casing 73 and the shaft 67 on which the bushing '72 is fixed. The longitudinal axis of the plunger 75 does not pass through the center of the shaft 67 but is slightly oil-set below that center as viewed in FIG. 5. Therefore the upper edge of the plunger 75 is nearer the bushing 72 than is the lower edge to define a slightly wedge shaped space between the bushing 72 and plunger 75.

When the casing 73 is rotated clockwise as viewed in FIG. 5, the sprag pin 74 which is greater in diameter than the minimum clearance between the plunger 75 and the bushing 72 is caused to grip the bushing and to rotate the shaft 67 with the rotation of the casing '73. This occurs because the sprag pin 74 is wedged tightly between the plunger 75 and the bushing 72 since it is caused to tend to move relatively toward the closed end of the wedge space between the plunger 75 and bushing 72. The amount of clockwise rotation is limited by the clearance between the pin 77 and the upper internal edge of the cavity in the casing 73. When the casing 73 is rotated in a counter-clockwise direction as viewed in FIG. 5, the sprag pin 74 is released and is only loosely held. The open end of the wedge space between the plunger 75 and bushing 72 is moved toward the sprag pin 74 with the counter-clockwise rotation. The spring loaded plunger 76 causes the pin 74 to follow back around the bushing 72 with the casing 73 until the pin 74 engages the fixed pin 77 which causes the plunger 76 to shift slightly and allow the pin 74 to stop slightly before the casing '73 is stopped. This moves the sprag pin 74 out of concurrent contact with the plunger 75 and the bushing 72. The pin 74- is then released in the wedge space between the plunger 75 and bushing 72 and the shaft 67 and bushing '72 may be freely rotated in either direction relative to the clutch mechanism 71.

There is a slight relative rotation between the bushing 72 and casing 73 which is required to move the clutch mechanism 71 from a released position to an engaging position. It is the difference between the point in the wedge space at which the pin 74 grips and at which it doesnt grip. The amount of movement required between release and engagement can be adjusted by moving the plunger 75 relative to the bushing 72 to increase or decrease the wedge space. This in effect is a sensitivity adjustment and the mechanism may be adjusted to the point where a very few thousandths of an inch of circumferential movement of the casing is all that is required.

The spring 81, FIG. 5, which is in compression between the casing 73 and the lower portion 43, tends to rotate the casing 73 counter-clockwise to the released position. A cam following roller 82 is rotatably fixed in the top of the clutch casing '73 (FIGS. 3, 5, 6). The roller 82 is engaged with a conical cam 33 which is fixed to a piston shaft 84. The piston shaft 84 is slidably received at one end on a cylinder bushing 85 that is fixed in the right side, as viewed in FIG. 6, of the lower portion 43. The other end of the piston shaft 84 is slidably received in a bushing 86 and is rotatable therewith since a key 87 is received therebetween. The bushing 86 is received in bearings 8d, 89 for rotation in the left side of the lower portion 48. A cap 94) is fixed to the bushing 86 and the knurled-head screw 91 is loosely received through the cap and is in threaded engagement through a flange portion of the bushing 86 to abut against a ring 92 fixed t0 the left side of the lower portion 48. When the screw 91 is tightened against the ring 92, the bushing 86 is locked against rotation. A plug 93 is received in one end of he bushing 556 against the cap 96. A spring 94 is compressed between the plug 93 and the end of the piston shaft 34. The spring 94 tends to hold the piston shaft to the right in the position shown in FIG. 6. In that position, the roller 82 is stopped by the cam 83 with the clutch 71 released. The clutch 71 is held in a released position by the spring 81 (FIG.

When hydraulic fiuid under pressure is connected to the cylinder bushing 85 at the right end (as viewed in FIG. 6) of the piston shaft 84, the spring 94 yields and the cam 83 is shifted left. The cam 83 is conical but is rotably adjustable on an axis that is parallel to one side of its surface when the bushing 86 is rotated with the piston shaft 84. As shown in FIG. 6, the upper side of the, cam 83 is parallel to the axis of rotation of the piston shaft 84. Therefore, the lower side of the cam is the most eccentric surface portion of the cam 83. As the cam 83 is moved left, it forces the roller 82 to move clockwise as viewed in FIGS. 5, 6 with the casing 73 of the clutch mechanism. As described, this moves the clutch 71 to an engaging position and imparts rotation to the tilt feed shaft 67. When pressure is disconnected from the cylinder bushing 85, the spring 9' returns the cam 83 to the position shown. The spring 81 rotates the clutch 71 to the released position at the same time. The shaft 67 remains in the angular position to which it is rotated by the clockwise rotation of the clutch 71.

When the shaft 67 is rotated clockwise as viewed in FIGS. 6 and 4, the eccentric diameter 67a of the shaft 67 raises the lever 63 which in turn raises the pin 62 to lift the rear end of the upper wheelhead portion 54 and to swing the grinding wheel 32 (FIG. 2) toward t 1@ table 12. The force between the lever 63 and eccentric diameter 67a created by the spring 66 is enough to produce a friction force to ensure that the shaft 67 will not rotate when the clutch 71 is released.

The shaft 67 must be rotated in the opposite direction (counter-clockwise as viewed in FIGS. 4, 5) to lower the lever 63 and to tilt the upper portion 54 away from the table 12. A gear 95 (FIG. 3) is fixed to the clutch bushing 72 to rotate with the shaft 67 and clutch bushing 72. A reset piston 96 (FIGS. 5, 8) extends transversely across the gear 35 and has a rack portion %a which en gages with the gear 95. The piston 96 is carried along to the left as viewed in FIG. 8 when the gear 95 is rotated clockwise with the shaft 67 by operation of the clutch 71. At some predetermined point in a machine cycle, the clutch 71 is stopped in its released position and the cam 83 is stopped. At this time the reset piston 96 may be shifted to the right, as viewed in FIG. 8, to rotate the shaft 67 counter-clockwise until the piston 96 engages the stop 97. The upper portion 54 is then tilted back down on the lower portion 48 to its starting position and the grinding wheel 32 is retracted from the table 12.

Thus it can be seen that the described feed mechanism is a high mechanical advantage device which will produce a series of very small steps or increments of movement of the grinding wheel 32 toward the work area. Since all of the components in the mechanism move quickly to produce each step, no detectable stick-slip is present in the tilt feed. In the embodiment of the machine described, a range of net tilt feed movement from .00025 inch per minute down to .000005 inch per minute is available. The total range of tilt feed movement in the machine is .001 inch. In sliding feed systems it is generally conceded that a feed of less than .0003 inch per minute is impractical.

The Coarse Pickfeed Mechanism The wheelhead 31) (FIGS. 1, 2) may be moved on the base 10 by rotation of the handwheel 411 which is fixed on the end of a shaft 98 (FIGS. 9, 11) which extends from the front of the machine at the base apron 42 into the rear base portion 1% below the wheelhead 31}. The end of the shaft 98 below the wheelhead 30 has one flat side 93a machined therealong. The end of the shaft 93 extends into a sleeve 99 which is rotatably received in bearings 1630, 1191. The bearings 1%, 1491 are fixed in 21 depending portion 48a. of the lower portion 43. The depending portion diia defines a yoke to which conventional sliding feed forces are transmitted to move the entire wheelhead 30. A pinion gear 102 is integral with the sleeve 19 and meshes with a gear 103. The gear 193 is fixed to rotate with a sleeve 104 by a key 105. The sleeve 1 94- is rotatably received in bearings 132, 133 which are fixed in the yoke 48a above the sleeve 99. The sleeve 1% is internally threaded and engaged with a feed screw 166. The feed screw 1% is not rotatable but axially movable when released from axial restraint. The screw 1% is not released for axial movement during coarse pickfeed. Therefore when the sleeve 104 is rotated, the Wheelhead 39 is forced to move on the ways 50, 52 (FIG. 10).

The sleeve 53% is adapted to loosely receive the flat sided end of the shaft 98. A roller collar 1117 is fixed to the end of the sleeve 99 by pins 108. The collar 1137 as a set of axles 119, 1111, 111, 51G. 10, spaced therearound and releasably fixed therein. One of the axles 199 has a journal diameter 111% on which a double ball bearing roller 112 is rotatably received. The roller 112 is engaged to straddle the flat surface 38a and to roll therealong as the shaft 98 and sleeve 29 are relatively axially moved as when the wheelhead 31) is moved on ways 5%, 52 (FIG. 10). The double roller 112 is held firmly in contact with the fiat surface 98a. by the singie ball bearing rollers 113, 11 2 which are rotatably received on the journal diameters 11th:, 111a of the axles 111 111. The rollers 113, 114 roll on the cylindrical surface of the shaft 9%. The journal diameters 163a, 1111a, 1110!. are all round but eccentric relative to the longitudinal axes of the axles 109, 110, 111. The axles are releasably held in the collar 1137 by set screws (not shown). When the axles 109, 110, 111 are released, they may be rotated to swing the eccentric diam.- eters 109, 1113a, 111a to bring the rollers 112, 113, 114- into forcible contact with the shaft 93. This preloads the rollers 112, 113, 114. Since the roller 112 is forcibly engaged with the fiat surface 986;, the roller 112 will transmit torque from the shaft 98 to the sleeve 99 and cause the sleeve 99 and shaft 98 to rotate in unison.

The shaft 98 may be rotated by the handwheel 41!, FIG. 11. Handwheel 4% may be manually driven or it may be rotated by means of a pick-feed mechanism as shown in FIGS. 11, 12. A toothed clutch member 115 is fixed by a key 116 to rotate with the shaft 93. A clutch bushing 117 is journaled over the clutch 115 and is rotatable relative thereto. A releasable overruning clutch mechanism 118 similar to the one 71 previously described in the tilt feed mechanism comprising a casing 119, a fixed pin 12%, and a sprag pin 121 is received over the bushing 117. The clearance within the clutch 118 is a fixed amount in this instance since the sprag pin 121 is received between the bushing 117 and a seat 122 fixed in the casing 119. A bell end pin 151 extends from the casing 119 and is received in a notch in a piston rod 123 which is reciprocated by a piston and cylinder motor 125. When the rod 123 is reciprocated, the casing 119 is reciprocally rotated. A counter-clockwise rotation of the casing 119 as viewed in FIG. 12 will force the sprag pin 121 to drive the bushing 117 in the same direction. As shown in FIG. 12, the rod 123 is moving downward to pull the casing 119 counter-clockwise. On reversal of movement of the rod 123, the casing is rotated clockwise until the fixed pin that is attached to the journal member 25 (FIG. 11) fixed in the base 10 moves the sprag pin 121 against the spring loaded plunger 126 to a released position. The amount that the casing is rotated depends upon the length of stroke of the rod 123. A spiral cam 127 is mounted on a shaft 128 which is rotatably adjustable from the machine front by the knob 129 (FIG. 1). The cam 127 is a stop which is engaged by the lower end of the piston rod 123 on its downward stroke. The length of the downward stroke of the rod 123 then is infinitely variable between the allowable extremes defined by the motor and the cam 127.

The rotation of the bushing 117 is transmitted to the handwheel 41 by the pin 131?, FIG. 11, which is fixed in the handwheel it? and received in the flange portion of the bushing 117. A clutch member 131 is fixed in the handwheel 40 over the shaft )8 which is loosely received in the handwheel 441. The clutch 131 mates with and drives the clutch 115 when the handwheel 41) is rotated. Since clutch 115 is fixed to the shaft 98, the incremental rotation of the bushing 117 by the clutch mechanism 118 and transmitted to the handwheel 41? is caused to rotate the shaft 98. This rotation of the shaft 38 results in a rotation of the sleeve 104 (FIG. 9) which will result in movement of the wheelhead 315 as dscribed. The pickfeed cycles of the particular machine described are gauge controlled and therefore no provision for automatic pickfeed reset is included in the feed mechanism exemplified. The pickfeed can be driven in reverse and would be retracted and reset by manual rotation of the handwheel 49.

T he Plunge Feed Mechanism The force which produces the plunge infeed for the described machine is produced in a backlash cylinder 134 shown in FIG. 13. Fluid under pressure is maintained at the right end of the piston 135 in the cylinder 134. The piston 135 pushes against a block 136 which is fixed to the rear of the lower wheelhead portion 48 (see also FIG. 3.) Thus a constant force is applied to the wheelhead 3t) tending to move it forward toward the table 12 (FIG. 2).

The feed mechanism shown in FIG. 14 acts as a brake to restrain movement of the wheelhead 3t) and to release it for movement at selected rates. The feed mechanism of FIG. 14 is of the type shown in US. Patent 2,718,101, issued September 20, 1955 on application filed by A. D. C. Stuckey and Jacob Decker. However, in this application, the mechanism is adapted to restrain the feed toward the table, the actual feed force toward the table being devel oped by the backlash cylinder 134 and piston 135 as described.

A collar 137 is fixed on a feed shaft 138 which is axially in line with the feed screw 1% (FIG. 9). The screw 160 is rigidly connected to the shaft 138 by coupling members 139, 140. The coupling members 139, 141) are attached to the ends of the screw 1116 and shaft 138, respectively, and are bolted together. The feed shaft 138 and screw 1196 are prevented from rotating by a pair of rollers 141 which are rotatably fixed to the feed box 38. The rollers 141 engage the flat sides of a tongue 142 extending radially from the shaft 138 and comprised of the two side members 142a, 1421) which are securely attached together and fixed to the end of the shaft 138. The shaft 138 is axially movable in the feed box 38. The force produced in the cylinder 134 tending to move the wheelhead 30 forward is transmitted to the shaft 138. The shaft 138 is restrained from moving by the walking beam 143 which is pivotally connected to the collar 137. The walking beam 143 is attached at one end to a piston 144 (FIG. 14). The other end is attached to a rotatable shaft 145. The piston 144 is normally held in the position shown by the application of fluid under pressure to its left end (as viewed in FIG. 14) through the fluid line 199. Upon connection of the low pressure to the left end of the piston 144 the end of the walking beam 143 attached thereto is allowed to swing to the left due to the pull from the wheelhead 30 created by the piston 135 and cylinder 134. The fluid leaves the space ahead of the piston 144 at a rapid rate and the shaft 138 and screw 1116 are shifted forward at a rapid rate for a fixed stroke. This allows the entire wheelhead 311 to advance toward the table 12 a fixed amount at a rapid rate.

After the completion of the rapid advance stroke, the shaft 145 is rotated by a piston 146 (FIG. 15 which is transverse to and below the shaft 145. The piston 146 has a rack 146a thereon which is engaged by a gear 147 that is fixed to the shaft 145 for rotation therewith. The shaft 145 has a threaded member 148 fixed thereto. The threaded member 148 is engaged through a nut 149. The nut 149 is fixed in the feed box 33. Therefore, the shaft 145 is moved axially during infeed. This movement is 10 from right to left (as viewed in FIG. 14) at a feed rate determined by the rate at which the piston 146 (FIG. 15) is moved.

The feed screw 106 is advanced a selected distance by the plunge infeed mechanism after the rapid advance stroke. At the end of the plunge infeed, the tilt feed mechanism described may be utilized to further feed the grinding wheel toward the worktable 12 to reduce a workpiece to the final selected size determined by the adjustment of the gauge unit 44. At the end of the grinding operation, pressure is again applied to the left end of the piston 144 and the piston 144 pulls the end of the walking beam 143 attached thereto back to the position shown. At the same time, the pressure fluid is connected to the piston 146 to reversely rotate the shaft 145. This returns the other end of the walking beam 143 to the retracted position shown. The walking beam 143 is returned against the force of the backlash cylinder 134.

Hydraulic Circuit The hydraulic operating circuit for the table 12 and pickfeed mechanism is shown in FIG. 16. A control lever 150 is connected by a gear 152 to rotate the spool 153 of a valve relative to a sleeve 155 fixed in the valve. The valve is indicated by sections 154a, 1541;. Prior to starting the machine cycle, the main pressure line 161 which connects with the source of pressure 156 (FIG. 15) is connected through section 154a to line 157 and also to line 158 through section 15411. This puts pressure on each side of the piston 15? in the motor 31 connected for movement of the table 12. There is no movement of the table 12 with the control circuit in this condition. When the lever 159 is rotated to the position indicated at 1511a, the spool 153 is rotated clockwise to connect lines 157 and 158 to lines 163, 164, respectively. Lines 163 and 164 connect with the table reversing valve 165. The direction of fluid under pressure from line 161 to lines 163, 164 is controlled by the position of the valve plunger 165a within the valve sleeve 16512. With plunger 165a in the position shown, pressure is connected to line 163. Line 163 is now connected to line 157. At this same time line 164 connects with line 166. Line 166 is connected through the pilot reversing valve 167 to line 168 which connects to the variable restriction rate valve 169 through which line 168 is connected to the main return line 162. The rate valve 169 controls the rate of fluid discharge from the line 168. Therefore, with the circuit in the condition described, the table 12 is moving to the right at a rate controlled by the setting of valve 169.

The position of the valve plunger 16512 is controlled by the position of the valve plunger 167a in the valve sleeve 167k. As shown, the plunger 167a is in its upper-most position and fluid is connected to the line 176 from line 161 through the valve 167. This pressure is applied through the variable restriction rate valve 171 to line 172 and from there to the upper end of the plunger 165a to hold it as shown. As the table 12 moves to the right, a dog 173 attached to the table 12 engages the reversing lever 174 to swing it clockwise as viewed in FIG. 16. Through the gearing 1'75, 176, the bell crank 177 is pivoted counter-clockwise to lower the plunger 167a to its lower-most position. Line 1711 is then connected to return line 162. Line 178 is connected to the main pressure line 161. Fluid line 17% connects with the variable restriction rate valve 179 which connects fluid under pressure to the line 130. Line 180 connects to the lower end of the plunger 165a. The plunger 165a begins to move upward at a rate controlled by the variable restriction 179. The fluid line 163 continues to be connected to pressure line 161 through valve 165 for a period of time while the plunger 165a is moving upward. At this same time, fluid pressure is connected from line 161 to line 166 through valve 167 whose plunger 167a has changed positions. Line 166 remains connected to line 164 for the brief time while line 163 is connected to the main pressure line 161.

Therefore both ends of the piston 159 are under pressure and the table 12 is stopped. The length of time that the table is stopped depends on the adjustment of the restriction 179. After a determinable time, the plunger 165a has moved upward to completely block line 163 from pressure line 161 and to begin to connect it to line 181. Line 181 connects through valve 167 at this time to line 168. At this same time line 164 is connected to line 161 through valve 154 and the piston 159 begins to move to the left. The fluid discharged ahead of the piston 159 from line 157 to line 163 to line 181 and to line 168 flows through the rate valve 169 to determine the rate of movement of the table 12 to the left.

At a predetermined point in movement to the left, another dog similar to the dog 173 engages the lever 174 and swings it back counter-clockwise and bell crank 177 moves the plunger 167a back upward to the position shown. The fluid pressure differential on the plunger 165 is reversed and the plunger moves back downward to the position shown at a rate determined by the setting of the restriction 171. The table 12 is stopped in a similar manner as described until the pressure connection from valve 165 to lines 163, 164 is reversed. By adjustment of the restrictions 171, 179, the amount of delay or tarry is variable at each end of a table stroke. It may be varied from a very short time to an extremely long time.

The pickfeed mechanism is controlled by the shift of the valve 167 at the reversing points. Fluid line 178 connects from the valve 167 to one end of the pickfeed pilot valve 182 as well as to the tarry rate valve 171. The fluid line 178 connects to the ultra fine feed reset valve 213 (FIG. and in the normal pick feed operation line 178 is connected to line 184 through that valve. Line 184 is connected to the other end of the valve 182 (FIG. 16). Both lines 178 and 184 are connected through dynamic resistances 185, 186, respectively, before connection to valve 182. Since lines 178 and 184 are connected through the dynamic resistances 185, 186, full pressure will not be connected through the line to the ends of the valve 182 while there is substantial flow of fluid through those lines. Main pressure line 161 also connects to the valve 182 at one side or the other of the large diameter land 182b depending on the end to which the spool 182a has shifted. In the position shown, the valve spool 182 will not shift against the force produced on the land 1232b until nearly full pressure is felt on its right end.

The operation of the valve 182 is as follows. Assume that the table 12 is moving away from the left toward the right reversing point and that valve 167 is in the condition shown in FIG. 16. As the table 12 reaches the right side reversing point, the lever 174 is swung to move the plunger 167a downward and pressure is connected to line 178 while line 1711 is connected to the low pressure return. Line 178 connects to line 184. At this same time, the line 184 is connected to line 187 through the valve 182. Line 187 is connected to the fluid line 188 through the selector valve 189 when the spool 189a is in the position shown. Line 188 connects to the piston and cylinder pickfeed motor 123 and the piston 191) is shifted away from the position shown to rotate the clutch casing 119 counter-clockwise to produce an increment of feed as previously described. The piston 190 moves since the resistance to movement is less than the resistance to shift of the plunger 182a offered by the force on the large diameter land 182E). The piston 198 moves until it engages the stop cam 127. When the piston 190 stops, the pressure in line 184 at the valve 182 rises due to the stopping of flow through the dynamic resistance 186. Suflicient force is then created on the spool 182a to shift it to its left end position (as viewed in FIG. 16). Line 187 is then connected to line 191 through valve 182. Line 191 is connected through the selector valve 189 to the main return line 162. Pressure is then taken off of the right end of the piston 191) (as viewed in FIG. 16). Line 184 is connected to line 192 through the valve 182 now and 12 line 192 connects directly to the motor 123 at the other end of the piston 191). Thus, the piston is shifted back to the position shown when the valve spool 182 shifts and the clutch casing 119 is rotated clockwise to the released position.

When the table 12 has moved back to the left and the pressure differential in lines 17 t1 and 184 has again changed the valve spool 182a changes immediately back to the position shown. This is so since the spool 189a blocks line 193 from line 191 and no pressure is connected from there to line 187 and from line 187 to line 188. Line 188 connects with the motor 123. The spool 182a then is in a position to cause pickfeed only at the right end reversing point of the table 12. The spool may be positioned in one of these other positions indicated at 194, 185, 196 in which pickfeed may be also produced at the left end of a table stroke and at both ends of a table stroke (1%). In the 4th position (194) no pickfeed is produced at all since the connections from line 187 to line 188 would be blocked completely to prevent a shift of the piston 1% away from the position shown. In the pick at left end position 195 of the spool 18%, the fluid line 1% would be connected to line 191 and pressure would be connected from line 178 between the resistance 185 and valve 182 to line 187 through the valve 182 at the instant of reversal of the table 12 from feed left to feed right (plunger 182a would be shifted to the left end of valve 182 at that instant). With the valve spool 189a in the pickfeed at both ends position 1%, the line 193 would connect through the valve 189 to line 197 and from there to line 191 when the table 12 reaches the left end reversal point. Line 187 would continue to connect through valve 189 to line 188 with the spool 188a in both the pickfeed at left end and at both ends positions. Line 184 would continue to connect through valve 182 to line 187. However, when the table reaches the right end reversing point when the spool is in the pickfeed at left end position 195, pressure would be felt on both ends of the piston 191) to prevent a shift of the piston to rotate the casing 11?. This is so since line 191 would be blocked by the spool 188a to prevent escape of fluid ahead of the piston 19%). Therefore pressure on one end of piston 19% would be applied to the other end by the piston 198 itself.

In FIG. 15, the hydraulic circuit for operation of the plunge feed mechanism of FIG. 14 is shown. The rapid advance valve 198 is operated by solenoid 2SOL. In the condition shown with solenoid ZSOL deenergized, pressure is connected from main pressure line 161 to line 199. Line 199 connects with the feed box 38 (FIG. 14) where it connects to the left end of the piston 144 to hold back against the previously described pull on fed shaft 138. When the solenoid ZSOL is energized, the spool 198a is shifted to the left and pressure is disconnected from line 199. Line 199 is then connected to the main return line 162. The piston 144 (FIG. 14) is moved rapidly to the left by the pull on feed shaft 138. Thus the rapid advance movement of the wheelhead is allowed.

Solenoid SSOL operates the plunge feed valve 288. In the deenergized condition, solenoid 5SOL allows the valve spool 28844 to be held in the position shown. Pressure from line 161 is then connected to the right end of the piston 14-6 from line 2111 which is connected to line 161 through valve 280. This holds the feed piston 146 in the feed retracted position. Upon the completion of a rapid advance stroke, the solenoid SSOL is energized to shift the plunger 28th: to the left. Line 201 is then connected to fluid line 282 which connects with line 283 through the dwell valve 204. Line 283 is connected with the slow rate valve 285. The fast feed cut-out valve 286 is operated by solenoid dSOL and solenoid dSOL is normally energized at the same time that the plunge feed valve 281) is first energized. Thus, line 282 is connected to line 2117 through the valve 206 past the spool idea which has now shifted left. Line 207 connects with the fast feed rate valve 208. Since the resistance to flow in rate valve 298 is less than in rate valve 205, most of the fluid from the right end of the piston 146 is discharged through valve 203 at a fast rate. The piston 146 is shifted to the right to force out the fluid since fluid line 2119 is connected to pressure line 161 through valve 2111) at this time. The piston 146 is then moved toward the right at a fast rate to rotate the gear 147 and shaft 145. The walking beam 143 (FIG. 14) is released for infeed movement at a fast rate as previously described herein.

After a predetermined amount of fast feed movement, the solenoid 4SOL is deenergized and fluid line 202 is disconnected from the fluid line 2117. The fluid leaving ahead of the piston 146 through line 201 is then returned by Way of rate valve 205 to line 162. The rate of rotation of the gear 147 and shaft 145 is reduced to reduce the feed rate of the wheelhead 39 (FIG. 2). After another predetermined movement of the wheelhead 12 at the slow rate, the solenoid 1SOL which operates valve 2114 is energized to shift the plunger 294a to the left to block line 202 from line 2113 thereby blocking the return flow of fluid from ahead of the piston 146. The plunge feed is then stopped.

At the same time that the solenoid 1SOL is energized, the tilt feed solenoid 6SOL and reset solenoid 7SOL are energized to operate the valves 211) and 213 to shift the plungers 210a and 21311 to the left. This connects fluid lines 211 and 212 and blocks line 215 from pressure line 161. Line 211 is connected to presure line 1611 around the ultra fine feed reset valve 213. Line 212 is connected through the dynamic resistance 214 tothe ultra fine feed cylinder bushing 85 (FIG. 6) to shift the cam 83 to the left (as viewed in FIG. 6). At the completion of one stroke of the cam 83, the solenoid 6SOL is deenergized and fluid line 212 is connected to the main return line 162 to allow the spring 94 to return the cam 83 to the right. Upon return of the cam 83 to the right, the solenoid 6SOL is reenergized to again stroke the cam 83 to the left. This reciprocating movement of the cam 83 produces tilt feed of the grinding wheel 32 (FIG. 2) in small steps as described.

When the grinding wheel 32 has been fed a predetermined amount and the workpiece has reached final size, the solenoid 6SOL is no longer energized and solenoid 7SOL is also deenergized. Solenoid 7SOL operates the reset valve 213. When deenergized, solenoid 7SOL allows the spool 213a to shift to the right to connect pressure line 161 to fluid line 215 which connects to the left end of the reset piston 96 (FIG. 8) to cause that piston to reset the ultra fine feed mechanism as previously described.

At the same time that solenoid 7SOL is deenergized to reset the ultra fine feed, solenoids ISOL, 2SOL, and SSOL are deenergized. This applies fluid under pressure to the rapid advice piston 144 at its left end as viewed in FIG. 14 through fluid line 129. Fluid under pressure is also applied to fluid line 2411 which connects with the right end of the feed piston 146 (FIG. 15) to return the feed shaft 145 to the position from which it started. Solenoid 4SOL was previously deenergized. The infeed plunge and retraction cycle is now completed.

In a traverse grinding operation, the rapid advance solenoid 2SOL is energized first to bring the Wheelhead 12 (FIG. 2) forward to a grinding position. The lever 150 is then swung counter-clockwise to begin the table traverse. The pickfeed mechanism operates as described at the selected reversing point or points. When the workpiece reaches a predetermined size, the reset valve spool 213a is shifted to the left by energization of solenoid 7SOL. This blocks the reversing line 184 from line 178 to the table reversing valve 167 (FIG. 16). Pressure is applied to line 184 :from line 161 through valve 213 and the pressure is connected through lines 187, 188 to hold the piston 1% to the left as viewed in FIG.

16. This stops the pickfeed. Line 178 continues to have the alternate connection to pressure and return through valve 167 since the table continues to reciprocate. This operates a plunger 126 which in turn operates a limit switch 9L8 which signals the solenoid 6SOL to energize at a selected end of the table stroke to produce a single reciprocation of the cam 83 (FIG. 6). The electrical circuit to be described in detail in the next section provides the control for the solenoid 6SOL which is dependent upon the operation of limit switch 9LS.

Electrical Control Circuit The schematic electrical control circuit shown in FIG. 17 controls the operation of the hydraulic actuating circuit described. A source of alternating current 219 supplies the power to the various control relays and contacts which are oriented on horizontal lines, the location of which is indicated by a number with the prefix L. The numbers run consecutively along the left side of the circuit. The locating reference will be given in parentheses with the circuit items as they are identified in the text to follow.

The master start relay 1M (L3) is connected across power lines 229, 221 and in series with the master start switch SW1 and master stop switch SW2. The master stop switch SW2 is normally closed while the master start switch SW1 is normally open. Closing switch SW1 results in the energizing of relay 1M and its latch contacts 1M-1 (L9) close to energize the hydraulic pump motor 222 (FIG. 15 The master start switch SW1 also has contacts in series with the grinding wheel motor start relay 2M (L111) which close at the same time that th switch SW1 is closed. A pressure switch 1P8 is also in series with the contacts of relay 2M and is actuated to close when the fluid pressure at the source (FIG. 15) reaches a predetermined level. The switch SW1 (L8, L11), FIG. 17) must be closed a second time after a period suflicient to allow the fluid pressure to build up and close the pressure switch 1P5. When the pressure switch 1P5 and switch SW1 are simultaneously closed, the relay 2M (L111) is energized. The relay 2M has contacts (not shown) which close in the power circuit to the grinding wheel motor 36 (FIGS. 1 and 2) to energize that motor and rotate the grinding wheel 32.

After allowing suflicient time for warm-up of the grinding wheel motor and hydraulic fluid, the machine is prepared for an automatic cycle. The first cycle to be described is a gauge controlled plunge grind operation in which the cycle of movement to grind a workpiece includes a rapid advance, a fast feed, a slow feed, a pause, and an ultra fine feed to final size. Upon the workpieces reaching final size, the grinding wheel is Withdrawn from the workpiece.

To prepare the machine circuit, the detented switch SW3 (L1?) in the energizing circuit for the headstock motor starting relay 4M is closed as shown. The relay 4M is not immediately energized since the circuit is not yet complete between the power lines 221 and 220a (connected to line 220 through the master stop switch SW2 and relay contacts 1M-1 at L9). The detented gauge energizing switch SW5 (L12) is also closed to energize the relay GCR and to apply power to the left side of the four sets of contacts ACR-l, BCR1, ACR2, BCR-Z (L13, L14, L15, L16, respectively) which are electrical contacts of the gauge unit 44 (FIG. 1) operated by the pneumatic relays included in the unit. The gauge cycle selector switch SW7 (FIG. 1), the contacts of which are shown only in part in FIG. 17, is set in a position to close contact SW7-5 (L17) to energize relay 109CR. At this time, the wheelhead feed mechanisms are in the re tracted and reset positions. The limit switch 4L8 (FIG. 15) is operated by the plunger 223 which is forced to the right (as viewed in FIG. 15 by pressure through fluid lines 224, 225, 226 in communication with the high pressure end of the piston 146. Limit switch 11LS (FIG. 3)

15 is operated by the dog 227 (FIGS. 3, 6) fixed in the end of the ultra fine feed shaft 67. Therefore the contacts 4LS-1 and 11LS-1 (L31, FIG. 17) are closed as shown and relay 7CR is energized. The machine is ready for a cycle and a workpiece is placed between the centers 22, 24 (FIG. 1) and engaged to be driven by the driver 28. The gauge calipers 46 are swung in position over the workpiece.

The cycle start switch SW8 (L22, FIG. 17) is closed instantaneously to start the grinding cycle. Relay 1CR is energized momentarily through the switch SW8 and the retract switch SWQ Relay ZCR (L23) is then energized through the contacts 7CR-1 and 1CR1 in the moment that relay ICR is energized. (Relay contacts are shown in the normal or relay deenergized condition, a normally closed contact being indicated by a slanting line through the contacts. Contacts of a relay are identified by the same reference symbols followed by a contact designator. Thuscontacts 1CR-1 are contacts of the relay 1CR). Relay ZCR latches in the energized condition, a circuit being completed through its own contacts ZCR-ll (L26) and the normally closed contacts ltM-CR-l. When relay ZCR is energized, solenoid ZSOL (L3 and FIG. 15) is energized through the contacts 2CR-2, ZCR3. This causes the rapid advance stroke of the wheelhead 39 as described in the hydraulic operation. At this same time, relay 116CR (L30, FIG. 17) is energized through the contacts 109CR-1, 1fi2CR-1 and ZCR-d. Thus the contacts 116CR-1 and 116CR-2 (L2) are opened to deenergize the solenoid 1SGL (also on FIG. 15) to prepare the hydraulic feed circuit for producing the fast and slow feed rates.

At the same time that the relay ZCR (L23) is energized and latched, the timing relay 1TR (L26) is energized and latched. The contacts 1TR1 (L26) are closed to complete the energizing circuit to relay 4M (L19) which starts the headstock motor 26 (FIG. 1) to rotate the driver 28. At the end of the rapid advance stroke, the limit switch 5L5 (FIG. 13) is operated by movement of the rod 228 which is attached to the dog 229 (FIG. 14). The dog 229 is attached to the rapid advance piston 144- for movement parallel therewith. The condition of the contacts 5LS-1 (L21) in reversed from the condition shown and the relay 3CR (L20) is energized through contacts SLS-l and latched through contacts 3CR-1 and 1TR-1. Relay SCR (L28) is also energized at this time since a circuit is complete through the contacts ZCR-S, 6CR-1, 18CR-1, ltlfiCR-Z and 101CR1 (L28). Solenoids SSOL and 4SOL (L5, L4, respectively, and in FIG. are energized through the contacts 3CR2, 3CR3 and SCR-l, SCR-Z. The hydraulic circuit is then conditioned to allow fast movement of the feed shaft 138 (FIG. 14) as previously described. The limit switch 4LS (FIG. 15) is then released and relay 7CR (L31) is deenergized.

Stock is removed from the workpiece during the fast feed movement and the gauge calipers 4-6 (FIG. 1) sense a change in size. When the workpiece reaches a predetermined size the first pressure operated switch contacts ACR-1- (L13) are closed and relay 1G1CR is energized. The relay contacts 101CR1 (L28) are opened and the relay SCR is deenergized. As the relay SCR is deenergized, so is the solenoid 4SOL (L4 and FIG. 15). The feed rate is reduced to a slow rate as described. Stock continues to be removed from the workpiece and when it reaches a second smaller predetermined size, the second pressure operated gauge contacts BCR1 (L14) close and relay 102CR is energized. The contacts ltiZCR-l (L30) are opened and relay 116CR is deenergized. When relay 116CR is deenergized the contacts 116CR-1 and 116CR-2 (L2) are closed and the solenoid ISOL (also FIG. 15) is energized. When solenoid 1SOL is energized, the hydraulic feed circuit is blocked to stop movement of the entire wheelhead 30 as a unit.

During the fast and slow feed movements of the wheelhead 36 (FIGS. 1, 2), pressure develops between the grinding wheel 32 and a workpiece. This pressure causes the machine parts and workpiece to spring slightly tending to move the workpiece and grinding wheel apart. When the feed is stopped, the pressure is gradually reduced. The workpiece and machine parts will return to their unstressed conditions. During this return, a small amount of stock will be removed from the workpiece since the workpiece and grinding wheel move toward one another when the described stresses are removed. The result is a further reduction in size of the workpiece. When the workpiece reaches a third predetermined small size, the third pressure operated gauge contacts ACR2 (L15) close to energize the relay 163CR.

At the time that the fast feed is first started, the ultra fine feed hydraulic circuit is prepared for operation. When relay 116011 (L319) is first picked up, the contacts 116CR 3 close and a circuit is completed through the contacts 116CR3, and ltiCsCR-l (L32) to energize relay 118CR (L37). Relay 118CR latches through the contacts 3CR4 and 11fiCR-1 (L33). Solenoid '7SOL (L7, and FIG. 15) is then energized and the pressure is taken off of the reset piston 96 (FIG. 8). When the relay NECK (L15) is energized, the relay 117CR (L32) is energized through the contacts ECR- i, llhCR-l, (L33), 18CR-2, 13LS-l,

. 1fi4CR-2, 12LS1, and llBCR-l (L35). The limit switch 13LS (FIG. 6) is operated by the ultra fine feed cam 83 in the retracted position as shown in FIG. 3 at the start of a feed stroke of the cam 83. Relay 11'7CR (L32) is latched energized around the switch contacts 13LS-1 through contacts 11'7CR-1 (L36) since the contacts 13LS- 1 (L35) open as soon as movement of the cam 83 is begun. The limit switch-12LS (FIG. 6) is operated by the cam 83 at the end of an ultra fine feed stroke and its operation opens contracts 12LS-1 (L35) to deenergize the relay 117CR (L32). The relay 11'7CR is not reenergized until limit switch 13LS is operated by the carn'83 at its starting position. When relay 117CR is energized, solenoid 6SOL (L6, and FIG. 15) is energized through contacts 117CR2, 11'7CR-3. When solenoid 6SOL is energized, fluid under pressure is connected to the right end of the piston shaft 84, as viewed in FIG. 6, to move it leftward. The described intermittent operation of the relay 117CR (L32) provides continued stroking of the cam 83 (FIG. 6) until the workpiece reaches final size, the feed now being provided in a succession of steps by operation of the described tilt feed mechanism. The net speed of the tilt feed per unit of time is greatly reduced from the rate of movement by the sliding feed mechanism.

The fourth pressure operated contacts BCR-Z (L16, FIG. 17) of the gauge unit 44, are closed when the workpiece reaches the predetermined final size. Relay 104CR (L16) is then energized and the contacts IMCR-Z (L35) are opened and relay 117CR (L32) is deenergized. With relay 117CR deenergized the solenoid 6SOL (L6) is deenergized also. The contacts 1-tl4-CR1 (L26) are also opened and relay ZCR (L23) is deenergized. Solenoid ZSOL (L3) is then deenergized and the wheelhead 30 (FIGS. 1, 2) is retracted rapidly due to pressure on the piston 144 (FIG. 14). RelayllTR (L26) is also deenergized when relay ltMCR (L16) is energized but the contacts 1TR-1 (L263) delay opening for a brief period before relays 4M (L19) and3CR (L20) are deenergized thereby, the limit switch contacts SLS-1 opening at the start of the rapid retraction stroke. Thus, the solenoid SSOL (L5) is held energized and the headstock motor 2t; (FIG. 1) continues to run until the rapid retraction is complete. The solenoid SSOL is then deenergized after the expiration of the delay period and the feed piston 146 is moved back to the position shown in FIG. 15. When relay 3CR is deenergized, the relay 113CR (L37) is deenergized also by the opening of contacts 3CR-4 (L33). The solenoid 7SOL (L7) is then deenergized by 

1. A GRINDING MACHINE COMPRISING: (A) A BASE HAVING A WORK SUPPORTING AREA AND WAYS THEREON EXTENDING TOWARD SAID AREA, (B) A WHEELHEAD MEMBER SLIDABLY RECEIVED ON SAID WAYS, (C) A SPINDLE HOUSING HAVING A ROTATABLE SPINDLE THEREIN, SAID SPINDLE HAVING A GRINDING WHEEL FIXED THERETO, (D) MEANS RESILIENTLY TO ATTACH SAID SPINDLE HOUSING TO SAID WHEELHEAD MEMBER, (E) A FEED MECHANISM SELECTIVELY TO MOVE SAID WHEELHEAD MEMBER ON SAID WAYS TOWARD SAID WORK SUPPORTING AREA FOR MOVEMENT OF SAID GRINDING WHEEL IN A CUTTING OPERATION, (F) MEANS SELECTIVELY TO OVERCOME SAID RESILIENT MEANS AND TILT SAID SPINDLE HOUSING ON SAID WHEELHEAD MEMBER IN STEPS TO PRODUCE MOVEMENT OF SAID GRINDING WHEEL RELATIVE TO SAID WHEELHEAD MEMBER TOWARD SAID WORK SUPPORTING AREA TO COMPLETE SAID CUTTING OPERATION, AND (G) MEANS REVERSELY TO OPERATE SAID FEED MECHANISM AND TO RESET SAID MEANS TO TILT TO RETRACT SAID GRINDING WHEEL FROM THE WORK SUPPORTING AREA UPON COMPLETION OF A CUTTING OPERATION. 